Synthetic vs. Felt Underlayment: What Lakeland Homeowners Should Know

When most people think about a new roof, they picture shingles, tiles, or metal panels — the stuff you can see from the street. But underneath all of that sits a layer that quietly does some of the heaviest lifting: the roofing underlayment. In Florida's climate, choosing the right underlayment isn't a minor detail. It's one of the more consequential decisions a homeowner and their contractor will make together.

If you're getting ready for a roof replacement or even a significant roof repair, understanding the difference between synthetic underlayment and traditional felt paper will help you ask the right questions and make sense of the bids you receive.

What Is Roofing Underlayment, Anyway?

Underlayment is a water-resistant or waterproof sheet material installed directly on the roof deck — the plywood or OSB sheathing — before the finish roofing material goes on. Think of it as a second line of defense: if wind-driven rain forces water past your shingles or tiles, the underlayment is what stands between that water and your home's interior.

There are two main categories in wide use today:

• Felt paper (asphalt-saturated felt): The traditional option, made from a base of organic or fiberglass mat saturated with asphalt. It comes in #15 and #30 weights, with heavier felt being thicker and more durable.
• Synthetic underlayment: A newer product made from woven or spun polypropylene or polyethylene. It's engineered specifically to outperform felt on most measurable dimensions.

Moisture Resistance

Florida's humidity is relentless. From June through September, afternoon downpours are practically scheduled, and even a brief gap in your roofing installation — say, an overnight delay — can expose your roof deck to real moisture risk.

Felt paper absorbs moisture. Wet felt can wrinkle, buckle, and temporarily lose some of its protective properties. If it stays wet for extended periods, it can even degrade or develop mold. In most Florida applications, #30 felt is the minimum practical choice over #15 precisely because it holds up a little better, but it's still a paper-based product with real limitations.

Synthetic underlayment, by contrast, repels moisture rather than absorbing it. It won't wrinkle, won't buckle when wet, and maintains its dimensional stability even if rain hits the open deck before the finish material is installed. For a climate where a passing storm can interrupt a multi-day roofing job, that stability matters.

Advantage: Synthetic

Wind Uplift Performance

This is where the Florida context becomes critical. The state's wind uplift requirements — governed by the Florida Building Code, which references ASCE 7 loading standards — are among the toughest in the country, especially in High-Velocity Hurricane Zones (HVHZ) that include Miami-Dade and Broward counties.

Felt paper tears relatively easily in high winds. Anyone who has watched felt flap off a roof deck during a storm knows how quickly it can fail. It also loses tensile strength when wet, which is exactly when you'd need it most.

Synthetic underlayments are significantly stronger. They're rated for much higher wind speeds and many carry Miami-Dade NOA (Notice of Acceptance) approvals, which are required for products used in the HVHZ. Even outside the HVHZ, a synthetic product with strong uplift ratings provides meaningful protection during storm damage events before help can arrive.

Advantage: Synthetic

Florida Building Code Compliance

Florida requires that underlayment products meet specific standards, and those standards have tightened considerably since Hurricane Andrew in 1992. The Florida Product Approval system means any underlayment used in the state must be tested and approved for use here — not just nationally listed.

Both felt and synthetic products can be Florida code-compliant, but not all of them are. The key is confirming that whatever product your contractor proposes carries a Florida Product Approval number. In HVHZ areas, a Miami-Dade NOA is required. Licensed contractors working under proper permits will know this, but it's worth asking about directly.

One nuance: some roofing systems — particularly certain tile roofs — specify required underlayment types in their system approval. Swapping underlayments without checking the system approval can inadvertently void the roofing system's compliance, even if both products are individually approved.

Bottom line: Compliance is achievable with both, but verify the specific product approval.

Longevity

Felt paper degrades over time, particularly under Florida's UV exposure and heat. If a finish roofing material ever needs to be partially removed for a repair underneath, old felt can crumble, tear, or otherwise fall apart — creating extra labor and cost.

Synthetic underlayments are far more UV-resistant and can typically be left exposed on the deck for 30 to 180 days (depending on the product) without significant degradation. They also tend to outlast the expected service life of the underlayment itself without becoming brittle.

Advantage: Synthetic

Cost

Here's where felt paper holds its ground. Traditional #30 felt is cheaper per square foot, and for budget-conscious projects, that difference can be meaningful across an entire roof.

Synthetic underlayment typically costs more upfront — sometimes noticeably so. However, when weighed against the performance advantages in a hurricane-prone, high-humidity climate like Florida's, many homeowners and contractors consider it money well spent. It's worth asking your contractor to quote both options and walk you through the tradeoff so you can decide what makes sense for your situation and budget.

Advantage: Felt (upfront cost only)

The Bottom Line for Lakeland Homeowners

For most homes in Lakeland, Florida, synthetic underlayment is the stronger performer across almost every category that matters in Florida — moisture resistance, wind uplift, longevity, and code performance in hurricane zones. Felt paper remains a legitimate, code-compliant option in some applications, particularly where budget is the primary constraint, but it carries real limitations in a climate this demanding.

The most important thing you can do is have this conversation directly with a licensed local roofer who knows Lakeland's specific code requirements and can recommend the right product for your roof system. You can also read more guides on our site to keep building your knowledge before that conversation happens.

Ready to get started? Call us and Lakeland Roof Co will connect you with a vetted, licensed local roofer in Lakeland who can perform a free inspection and walk you through your underlayment options with no pressure and no obligation.